/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_iir_lattice_q15.c
*
* Description:	Q15 IIR lattice filter processing function.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
*     the documentation and/or other materials provided with the
*     distribution.
*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup IIR_Lattice
 * @{
 */

/**
 * @brief Processing function for the Q15 IIR lattice filter.
 * @param[in] *S points to an instance of the Q15 IIR lattice structure.
 * @param[in] *pSrc points to the block of input data.
 * @param[out] *pDst points to the block of output data.
 * @param[in] blockSize number of samples to process.
 * @return none.
 *
 * @details
 * <b>Scaling and Overflow Behavior:</b>
 * \par
 * The function is implemented using a 64-bit internal accumulator.
 * Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result.
 * The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.
 * There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.
 * After all additions have been performed, the accumulator is truncated to 34.15 format by discarding low 15 bits.
 * Lastly, the accumulator is saturated to yield a result in 1.15 format.
 */

void arm_iir_lattice_q15(
    const arm_iir_lattice_instance_q15 *S,
    q15_t *pSrc,
    q15_t *pDst,
    uint32_t blockSize)
{


#ifndef ARM_MATH_CM0_FAMILY

    /* Run the below code for Cortex-M4 and Cortex-M3 */

    q31_t fcurr, fnext, gcurr = 0, gnext;          /* Temporary variables for lattice stages */
    q15_t gnext1, gnext2;                          /* Temporary variables for lattice stages */
    uint32_t stgCnt;                               /* Temporary variables for counts */
    q63_t acc;                                     /* Accumlator */
    uint32_t blkCnt, tapCnt;                       /* Temporary variables for counts */
    q15_t *px1, *px2, *pk, *pv;                    /* temporary pointers for state and coef */
    uint32_t numStages = S->numStages;             /* number of stages */
    q15_t *pState;                                 /* State pointer */
    q15_t *pStateCurnt;                            /* State current pointer */
    q15_t out;                                     /* Temporary variable for output */
    q31_t v;                                       /* Temporary variable for ladder coefficient */
#ifdef UNALIGNED_SUPPORT_DISABLE
    q15_t v1, v2;
#endif


    blkCnt = blockSize;

    pState = &S->pState[0];

    /* Sample processing */
    while(blkCnt > 0u)
    {
        /* Read Sample from input buffer */
        /* fN(n) = x(n) */
        fcurr = *pSrc++;

        /* Initialize state read pointer */
        px1 = pState;
        /* Initialize state write pointer */
        px2 = pState;
        /* Set accumulator to zero */
        acc = 0;
        /* Initialize Ladder coeff pointer */
        pv = &S->pvCoeffs[0];
        /* Initialize Reflection coeff pointer */
        pk = &S->pkCoeffs[0];


        /* Process sample for first tap */
        gcurr = *px1++;
        /* fN-1(n) = fN(n) - kN * gN-1(n-1) */
        fnext = fcurr - (((q31_t) gcurr * (*pk)) >> 15);
        fnext = __SSAT(fnext, 16);
        /* gN(n) = kN * fN-1(n) + gN-1(n-1) */
        gnext = (((q31_t) fnext * (*pk++)) >> 15) + gcurr;
        gnext = __SSAT(gnext, 16);
        /* write gN(n) into state for next sample processing */
        *px2++ = (q15_t) gnext;
        /* y(n) += gN(n) * vN  */
        acc += (q31_t) ((gnext * (*pv++)));


        /* Update f values for next coefficient processing */
        fcurr = fnext;

        /* Loop unrolling.  Process 4 taps at a time. */
        tapCnt = (numStages - 1u) >> 2;

        while(tapCnt > 0u)
        {

            /* Process sample for 2nd, 6th ...taps */
            /* Read gN-2(n-1) from state buffer */
            gcurr = *px1++;
            /* Process sample for 2nd, 6th .. taps */
            /* fN-2(n) = fN-1(n) - kN-1 * gN-2(n-1) */
            fnext = fcurr - (((q31_t) gcurr * (*pk)) >> 15);
            fnext = __SSAT(fnext, 16);
            /* gN-1(n) = kN-1 * fN-2(n) + gN-2(n-1) */
            gnext = (((q31_t) fnext * (*pk++)) >> 15) + gcurr;
            gnext1 = (q15_t) __SSAT(gnext, 16);
            /* write gN-1(n) into state */
            *px2++ = (q15_t) gnext1;


            /* Process sample for 3nd, 7th ...taps */
            /* Read gN-3(n-1) from state */
            gcurr = *px1++;
            /* Process sample for 3rd, 7th .. taps */
            /* fN-3(n) = fN-2(n) - kN-2 * gN-3(n-1) */
            fcurr = fnext - (((q31_t) gcurr * (*pk)) >> 15);
            fcurr = __SSAT(fcurr, 16);
            /* gN-2(n) = kN-2 * fN-3(n) + gN-3(n-1) */
            gnext = (((q31_t) fcurr * (*pk++)) >> 15) + gcurr;
            gnext2 = (q15_t) __SSAT(gnext, 16);
            /* write gN-2(n) into state */
            *px2++ = (q15_t) gnext2;

            /* Read vN-1 and vN-2 at a time */
#ifndef UNALIGNED_SUPPORT_DISABLE

            v = *__SIMD32(pv)++;

#else

            v1 = *pv++;
            v2 = *pv++;

#ifndef ARM_MATH_BIG_ENDIAN

            v = __PKHBT(v1, v2, 16);

#else

            v = __PKHBT(v2, v1, 16);

#endif	/* 	#ifndef ARM_MATH_BIG_ENDIAN		*/

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE */


            /* Pack gN-1(n) and gN-2(n) */

#ifndef  ARM_MATH_BIG_ENDIAN

            gnext = __PKHBT(gnext1, gnext2, 16);

#else

            gnext = __PKHBT(gnext2, gnext1, 16);

#endif /*   #ifndef  ARM_MATH_BIG_ENDIAN    */

            /* y(n) += gN-1(n) * vN-1  */
            /* process for gN-5(n) * vN-5, gN-9(n) * vN-9 ... */
            /* y(n) += gN-2(n) * vN-2  */
            /* process for gN-6(n) * vN-6, gN-10(n) * vN-10 ... */
            acc = __SMLALD(gnext, v, acc);


            /* Process sample for 4th, 8th ...taps */
            /* Read gN-4(n-1) from state */
            gcurr = *px1++;
            /* Process sample for 4th, 8th .. taps */
            /* fN-4(n) = fN-3(n) - kN-3 * gN-4(n-1) */
            fnext = fcurr - (((q31_t) gcurr * (*pk)) >> 15);
            fnext = __SSAT(fnext, 16);
            /* gN-3(n) = kN-3 * fN-1(n) + gN-1(n-1) */
            gnext = (((q31_t) fnext * (*pk++)) >> 15) + gcurr;
            gnext1 = (q15_t) __SSAT(gnext, 16);
            /* write  gN-3(n) for the next sample process */
            *px2++ = (q15_t) gnext1;


            /* Process sample for 5th, 9th ...taps */
            /* Read gN-5(n-1) from state */
            gcurr = *px1++;
            /* Process sample for 5th, 9th .. taps */
            /* fN-5(n) = fN-4(n) - kN-4 * gN-5(n-1) */
            fcurr = fnext - (((q31_t) gcurr * (*pk)) >> 15);
            fcurr = __SSAT(fcurr, 16);
            /* gN-4(n) = kN-4 * fN-5(n) + gN-5(n-1) */
            gnext = (((q31_t) fcurr * (*pk++)) >> 15) + gcurr;
            gnext2 = (q15_t) __SSAT(gnext, 16);
            /* write      gN-4(n) for the next sample process */
            *px2++ = (q15_t) gnext2;

            /* Read vN-3 and vN-4 at a time */
#ifndef UNALIGNED_SUPPORT_DISABLE

            v = *__SIMD32(pv)++;

#else

            v1 = *pv++;
            v2 = *pv++;

#ifndef ARM_MATH_BIG_ENDIAN

            v = __PKHBT(v1, v2, 16);

#else

            v = __PKHBT(v2, v1, 16);

#endif	/* #ifndef ARM_MATH_BIG_ENDIAN	 */

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE */


            /* Pack gN-3(n) and gN-4(n) */
#ifndef  ARM_MATH_BIG_ENDIAN

            gnext = __PKHBT(gnext1, gnext2, 16);

#else

            gnext = __PKHBT(gnext2, gnext1, 16);

#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */

            /* y(n) += gN-4(n) * vN-4  */
            /* process for gN-8(n) * vN-8, gN-12(n) * vN-12 ... */
            /* y(n) += gN-3(n) * vN-3  */
            /* process for gN-7(n) * vN-7, gN-11(n) * vN-11 ... */
            acc = __SMLALD(gnext, v, acc);

            tapCnt--;

        }

        fnext = fcurr;

        /* If the filter length is not a multiple of 4, compute the remaining filter taps */
        tapCnt = (numStages - 1u) % 0x4u;

        while(tapCnt > 0u)
        {
            gcurr = *px1++;
            /* Process sample for last taps */
            fnext = fcurr - (((q31_t) gcurr * (*pk)) >> 15);
            fnext = __SSAT(fnext, 16);
            gnext = (((q31_t) fnext * (*pk++)) >> 15) + gcurr;
            gnext = __SSAT(gnext, 16);
            /* Output samples for last taps */
            acc += (q31_t) (((q31_t) gnext * (*pv++)));
            *px2++ = (q15_t) gnext;
            fcurr = fnext;

            tapCnt--;
        }

        /* y(n) += g0(n) * v0 */
        acc += (q31_t) (((q31_t) fnext * (*pv++)));

        out = (q15_t) __SSAT(acc >> 15, 16);
        *px2++ = (q15_t) fnext;

        /* write out into pDst */
        *pDst++ = out;

        /* Advance the state pointer by 4 to process the next group of 4 samples */
        pState = pState + 1u;
        blkCnt--;

    }

    /* Processing is complete. Now copy last S->numStages samples to start of the buffer
       for the preperation of next frame process */
    /* Points to the start of the state buffer */
    pStateCurnt = &S->pState[0];
    pState = &S->pState[blockSize];

    stgCnt = (numStages >> 2u);

    /* copy data */
    while(stgCnt > 0u)
    {
#ifndef UNALIGNED_SUPPORT_DISABLE

        *__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
        *__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;

#else

        *pStateCurnt++ = *pState++;
        *pStateCurnt++ = *pState++;
        *pStateCurnt++ = *pState++;
        *pStateCurnt++ = *pState++;

#endif /*	#ifndef UNALIGNED_SUPPORT_DISABLE */

        /* Decrement the loop counter */
        stgCnt--;

    }

    /* Calculation of count for remaining q15_t data */
    stgCnt = (numStages) % 0x4u;

    /* copy data */
    while(stgCnt > 0u)
    {
        *pStateCurnt++ = *pState++;

        /* Decrement the loop counter */
        stgCnt--;
    }

#else

    /* Run the below code for Cortex-M0 */

    q31_t fcurr, fnext = 0, gcurr = 0, gnext;      /* Temporary variables for lattice stages */
    uint32_t stgCnt;                               /* Temporary variables for counts */
    q63_t acc;                                     /* Accumlator */
    uint32_t blkCnt, tapCnt;                       /* Temporary variables for counts */
    q15_t *px1, *px2, *pk, *pv;                    /* temporary pointers for state and coef */
    uint32_t numStages = S->numStages;             /* number of stages */
    q15_t *pState;                                 /* State pointer */
    q15_t *pStateCurnt;                            /* State current pointer */
    q15_t out;                                     /* Temporary variable for output */


    blkCnt = blockSize;

    pState = &S->pState[0];

    /* Sample processing */
    while(blkCnt > 0u)
    {
        /* Read Sample from input buffer */
        /* fN(n) = x(n) */
        fcurr = *pSrc++;

        /* Initialize state read pointer */
        px1 = pState;
        /* Initialize state write pointer */
        px2 = pState;
        /* Set accumulator to zero */
        acc = 0;
        /* Initialize Ladder coeff pointer */
        pv = &S->pvCoeffs[0];
        /* Initialize Reflection coeff pointer */
        pk = &S->pkCoeffs[0];

        tapCnt = numStages;

        while(tapCnt > 0u)
        {
            gcurr = *px1++;
            /* Process sample */
            /* fN-1(n) = fN(n) - kN * gN-1(n-1) */
            fnext = fcurr - ((gcurr * (*pk)) >> 15);
            fnext = __SSAT(fnext, 16);
            /* gN(n) = kN * fN-1(n) + gN-1(n-1) */
            gnext = ((fnext * (*pk++)) >> 15) + gcurr;
            gnext = __SSAT(gnext, 16);
            /* Output samples */
            /* y(n) += gN(n) * vN */
            acc += (q31_t) ((gnext * (*pv++)));
            /* write gN(n) into state for next sample processing */
            *px2++ = (q15_t) gnext;
            /* Update f values for next coefficient processing */
            fcurr = fnext;

            tapCnt--;
        }

        /* y(n) += g0(n) * v0 */
        acc += (q31_t) ((fnext * (*pv++)));

        out = (q15_t) __SSAT(acc >> 15, 16);
        *px2++ = (q15_t) fnext;

        /* write out into pDst */
        *pDst++ = out;

        /* Advance the state pointer by 1 to process the next group of samples */
        pState = pState + 1u;
        blkCnt--;

    }

    /* Processing is complete. Now copy last S->numStages samples to start of the buffer
       for the preperation of next frame process */
    /* Points to the start of the state buffer */
    pStateCurnt = &S->pState[0];
    pState = &S->pState[blockSize];

    stgCnt = numStages;

    /* copy data */
    while(stgCnt > 0u)
    {
        *pStateCurnt++ = *pState++;

        /* Decrement the loop counter */
        stgCnt--;
    }

#endif /*   #ifndef ARM_MATH_CM0_FAMILY */

}




/**
 * @} end of IIR_Lattice group
 */
